IT博客汇 | [转]C++ 如何：在各种字符串类型之间进行转换

[转]C++ 如何：在各种字符串类型之间进行转换

lincyang发表于 2011-01-06 10:18:00

本文是从msdn上转过来的，写的非常全面了。

http://msdn.microsoft.com/zh-cn/library/ms235631(v=vs.80).aspx

本主题演示如何将各种 Visual C++ 字符串类型转换为其他字符串。可以转换的字符串类型包括 char*、wchar_t*、_bstr_t、CComBSTR、CString、basic_string 和 System.String。在所有情况下，在将字符串转换为新类型时，都会创建字符串的副本。对新字符串进行的任何更改都不会影响原始字符串，反之亦然。

1、此示例演示如何从 char * 转换为上面列出的其他字符串类型。

// convert_from_char.cpp // compile with: /clr /link comsuppw.lib #include <iostream> #include <stdlib.h> #include <string> #include "atlbase.h" #include "atlstr.h" #include "comutil.h" using namespace std; using namespace System; int main() { char *orig = "Hello, World!"; cout << orig << " (char *)" << endl; // Convert to a wchar_t* size_t origsize = strlen(orig) + 1; const size_t newsize = 100; size_t convertedChars = 0; wchar_t wcstring[newsize]; mbstowcs_s(&convertedChars, wcstring, origsize, orig, _TRUNCATE); wcscat_s(wcstring, L" (wchar_t *)"); wcout << wcstring << endl; // Convert to a _bstr_t _bstr_t bstrt(orig); bstrt += " (_bstr_t)"; cout << bstrt << endl; // Convert to a CComBSTR CComBSTR ccombstr(orig); if (ccombstr.Append(L" (CComBSTR)") == S_OK) { CW2A printstr(ccombstr); cout << printstr << endl; } // Convert to a CString CString cstring(orig); cstring += " (CString)"; cout << cstring << endl; // Convert to a basic_string string basicstring(orig); basicstring += " (basic_string)"; cout << basicstring << endl; // Convert to a System::String String ^systemstring = gcnew String(orig); systemstring += " (System::String)"; Console::WriteLine("{0}", systemstring); delete systemstring; }

输出

Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CString)
Hello, World! (basic_string)
Hello, World! (System::String)

2、此示例演示如何从 wchar_t * 转换为上面列出的其他字符串类型。

// convert_from_wchar_t.cpp
// compile with: /clr /link comsuppw.lib

#include <iostream>
#include <stdlib.h>
#include <string>

#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"

using namespace std;
using namespace System;

int main()
{
    wchar_t *orig = L"Hello, World!";
    wcout << orig << L" (wchar_t *)" << endl;

    // Convert to a char*
    size_t origsize = wcslen(orig) + 1;
    const size_t newsize = 100;
    size_t convertedChars = 0;
    char nstring[newsize];
    wcstombs_s(&convertedChars, nstring, origsize, orig, _TRUNCATE);
    strcat_s(nstring, " (char *)");
    cout << nstring << endl;

    // Convert to a _bstr_t
    _bstr_t bstrt(orig);
    bstrt += " (_bstr_t)";
    cout << bstrt << endl;

    // Convert to a CComBSTR
    CComBSTR ccombstr(orig);
    if (ccombstr.Append(L" (CComBSTR)") == S_OK)
    {
        CW2A printstr(ccombstr);
        cout << printstr << endl;
    }

    // Convert to a CString
    CString cstring(orig);
    cstring += " (CString)";
    cout << cstring << endl;

    // Convert to a basic_string
    wstring basicstring(orig);
    basicstring += L" (basic_string)";
    wcout << basicstring << endl;

    // Convert to a System::String
    String ^systemstring = gcnew String(orig);
    systemstring += " (System::String)";
    Console::WriteLine("{0}", systemstring);
    delete systemstring;
}

输出
Hello, World! (wchar_t *)
Hello, World! (char *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CString)
Hello, World! (basic_string)
Hello, World! (System::String)
3、此示例演示如何从 _bstr_t 转换为上面列出的其他字符串类型。
// convert_from_bstr_t.cpp
// compile with: /clr /link comsuppw.lib

#include <iostream>
#include <stdlib.h>
#include <string>

#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"

using namespace std;
using namespace System;

int main()
{
    _bstr_t orig("Hello, World!");
    wcout << orig << " (_bstr_t)" << endl;

    // Convert to a char*
    const size_t newsize = 100;
    char nstring[newsize];
    strcpy_s(nstring, (char *)orig);
    strcat_s(nstring, " (char *)");
    cout << nstring << endl;

    // Convert to a wchar_t*
    wchar_t wcstring[newsize];
    wcscpy_s(wcstring, (wchar_t *)orig);
    wcscat_s(wcstring, L" (wchar_t *)");
    wcout << wcstring << endl;

    // Convert to a CComBSTR
    CComBSTR ccombstr((char *)orig);
    if (ccombstr.Append(L" (CComBSTR)") == S_OK)
    {
        CW2A printstr(ccombstr);
        cout << printstr << endl;
    }

    // Convert to a CString
    CString cstring((char *)orig);
    cstring += " (CString)";
    cout << cstring << endl;

    // Convert to a basic_string
    string basicstring((char *)orig);
    basicstring += " (basic_string)";
    cout << basicstring << endl;

    // Convert to a System::String
    String ^systemstring = gcnew String((char *)orig);
    systemstring += " (System::String)";
    Console::WriteLine("{0}", systemstring);
    delete systemstring;
} 
输出
Hello, World! (_bstr_t)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (CComBSTR)
Hello, World! (CString)
Hello, World! (basic_string)
Hello, World! (System::String)
4、此示例演示如何从 CComBSTR 转换为上面列出的其他字符串类型。
// convert_from_ccombstr.cpp
// compile with: /clr /link comsuppw.lib

#include <iostream>
#include <stdlib.h>
#include <string>

#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
#include "vcclr.h"

using namespace std;
using namespace System;
using namespace System::Runtime::InteropServices;

int main()
{
    CComBSTR orig("Hello, World!");
    CW2A printstr(orig);
    cout << printstr << " (CComBSTR)" << endl;

    // Convert to a char*
    const size_t newsize = 100;
    char nstring[newsize];
    CW2A tmpstr1(orig);
    strcpy_s(nstring, tmpstr1);
    strcat_s(nstring, " (char *)");
    cout << nstring << endl;

    // Convert to a wchar_t*
    wchar_t wcstring[newsize];
    wcscpy_s(wcstring, orig);
    wcscat_s(wcstring, L" (wchar_t *)");
    wcout << wcstring << endl;

    // Convert to a _bstr_t
    _bstr_t bstrt(orig);
    bstrt += " (_bstr_t)";
    cout << bstrt << endl;

    // Convert to a CString
    CString cstring(orig);
    cstring += " (CString)";
    cout << cstring << endl;

    // Convert to a basic_string
    wstring basicstring(orig);
    basicstring += L" (basic_string)";
    wcout << basicstring << endl;

    // Convert to a System::String
    String ^systemstring = gcnew String(orig);
    systemstring += " (System::String)";
    Console::WriteLine("{0}", systemstring);
    delete systemstring;
} 
输出
Hello, World! (CComBSTR)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CString)
Hello, World! (basic_string)
Hello, World! (System::String)
5、此示例演示如何从 CString 转换为上面列出的其他字符串类型。
// convert_from_cstring.cpp
// compile with: /clr /link comsuppw.lib

#include <iostream>
#include <stdlib.h>
#include <string>

#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"

using namespace std;
using namespace System;

int main()
{
    CString orig("Hello, World!");
    wcout << orig << " (CString)" << endl;

    // Convert to a char*
    const size_t newsize = 100;
    char nstring[newsize];
    strcpy_s(nstring, orig);
    strcat_s(nstring, " (char *)");
    cout << nstring << endl;

    // Convert to a wchar_t*
    // You must first convert to a char * for this to work.
    size_t origsize = strlen(orig) + 1;
    size_t convertedChars = 0;
    wchar_t wcstring[newsize];
    mbstowcs_s(&convertedChars, wcstring, origsize, orig, _TRUNCATE);
    wcscat_s(wcstring, L" (wchar_t *)");
    wcout << wcstring << endl;

    // Convert to a _bstr_t
    _bstr_t bstrt(orig);
    bstrt += " (_bstr_t)";
    cout << bstrt << endl;

    // Convert to a CComBSTR
    CComBSTR ccombstr(orig);
    if (ccombstr.Append(L" (CComBSTR)") == S_OK)
    {
        CW2A printstr(ccombstr);
        cout << printstr << endl;
    }

    // Convert to a basic_string
    string basicstring(orig);
    basicstring += " (basic_string)";
    cout << basicstring << endl;

    // Convert to a System::String
    String ^systemstring = gcnew String(orig);
    systemstring += " (System::String)";
    Console::WriteLine("{0}", systemstring);
    delete systemstring;
} 
输出
Hello, World! (CString)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (basic_string)
Hello, World! (System::String)
6、此示例演示如何从 basic_string 转换为上面列出的其他字符串类型。
// convert_from_basic_string.cpp
// compile with: /clr /link comsuppw.lib

#include <iostream>
#include <stdlib.h>
#include <string>

#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"

using namespace std;
using namespace System;

int main()
{
    string orig("Hello, World!");
    cout << orig << " (basic_string)" << endl;

    // Convert to a char*
    const size_t newsize = 100;
    char nstring[newsize];
    strcpy_s(nstring, orig.c_str());
    strcat_s(nstring, " (char *)");
    cout << nstring << endl;

    // Convert to a wchar_t*
    // You must first convert to a char * for this to work.
    size_t origsize = strlen(orig.c_str()) + 1;
    size_t convertedChars = 0;
    wchar_t wcstring[newsize];
    mbstowcs_s(&convertedChars, wcstring, origsize, orig.c_str(), _TRUNCATE);
    wcscat_s(wcstring, L" (wchar_t *)");
    wcout << wcstring << endl;

    // Convert to a _bstr_t
    _bstr_t bstrt(orig.c_str());
    bstrt += " (_bstr_t)";
    cout << bstrt << endl;

    // Convert to a CComBSTR
    CComBSTR ccombstr(orig.c_str());
    if (ccombstr.Append(L" (CComBSTR)") == S_OK)
    {
        CW2A printstr(ccombstr);
        cout << printstr << endl;
    }

    // Convert to a CString
    CString cstring(orig.c_str());
    cstring += " (CString)";
    cout << cstring << endl;

    // Convert to a System::String
    String ^systemstring = gcnew String(orig.c_str());
    systemstring += " (System::String)";
    Console::WriteLine("{0}", systemstring);
    delete systemstring;
} 
输出
Hello, World! (basic_string)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CString)
Hello, World! (System::String)
7、此示例演示如何从 System.String 转换为上面列出的其他字符串类型。
// convert_from_system_string.cpp
// compile with: /clr /link comsuppw.lib

#include <iostream>
#include <stdlib.h>
#include <string>

#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
#include "vcclr.h"

using namespace std;
using namespace System;
using namespace System::Runtime::InteropServices;

int main()
{
    String ^orig = gcnew String("Hello, World!");
    Console::WriteLine("{0} (System::String)", orig);

    pin_ptr<const wchar_t> wch = PtrToStringChars(orig);

    // Convert to a char*
    size_t origsize = wcslen(wch) + 1;
    const size_t newsize = 100;
    size_t convertedChars = 0;
    char nstring[newsize];
    wcstombs_s(&convertedChars, nstring, origsize, wch, _TRUNCATE);
    strcat_s(nstring, " (char *)");
    cout << nstring << endl;

    // Convert to a wchar_t*
    wchar_t wcstring[newsize];
    wcscpy_s(wcstring, wch);
    wcscat_s(wcstring, L" (wchar_t *)");
    wcout << wcstring << endl;

    // Convert to a _bstr_t
    _bstr_t bstrt(wch);
    bstrt += " (_bstr_t)";
    cout << bstrt << endl;

    // Convert to a CComBSTR
    CComBSTR ccombstr(wch);
    if (ccombstr.Append(L" (CComBSTR)") == S_OK)
    {
        CW2A printstr(ccombstr);
        cout << printstr << endl;
    }

    // Convert to a CString
    CString cstring(wch);
    cstring += " (CString)";
    cout << cstring << endl;

    // Convert to a basic_string
    wstring basicstring(wch);
    basicstring += L" (basic_string)";
    wcout << basicstring << endl;

    delete orig;
} 
输出
Hello, World! (System::String)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CString)
Hello, World! (basic_string)

关于_viriant_t和std::string之间的转换
#include <comutil.h>
#include <string>

std::string from_variant(VARIANT& vt)
{
_bstr_t bs(vt);
return std::string(static_cast<const char*>(bs));
}

void to_variant(const std::string& str, VARIANT& vt)
{
_bstr_t bs(str.c_str());
reinterpret_cast<_variant_t&>(vt) = bs;
}